IDT, GDT, LDT and other about the memory

[Unexpected]

Hi,
Can anyone help or give me a link about IDT, GDT, LDT and other....
I wan't understand whats that and how it works...
And how use this...

Please help.. Thanx you!

[Elfredo]

Hi,

there is a tutorial along with some source code about Protected Mode on this site. But for an in-depth explanation i would recommend the intel docs (especially intel 386 programmers reference volume 3), also avaible on the site.

http://my.execpc.com/CE/AC/geezer/os/

[K.J.]

From http://osdev.neopages.net/tutorials/gettingstarted.php:

Q: What is a GDT?

A: A gdt is a table containing selectors. Basically it provides a starting address to address all selectors.

Q: What is a selector?

A: A selector(sometimes also called a descriptor) is a definition of a segment. It contains a description of basic segment attributes, like the segment base (it's starting address) and the segments limit (it's length). Each selector is 64 bits long. More about them in the description of a GDT and LDT.

K.J.

[Perica]

..

[jrfritz]

Local Descriptor Table.

It's for hardware multitasking...right?

[K.J.]

It's for hardware multitasking...right?

No, the LDT is so each process/thread can have it's own 'mini' GDT' sorta. It works with software or hardware multitasking.

K.J.

[Pype.Clicker]

It's for hardware multitasking...right?

somehow, it is ... As each TSS can be given a personnal LDT, you can enforce more protection within the same address space if you give separated TSS separated LDTs. You can even use it in a software or hybrid multitasking if you have used segments or call/task gates somewhere and don't want every process to get the same priviledge access ...